Only split CSV in the client, quote instead of escaping

Splitting on commas is not an idempotent operation:
'a,b\,c' -> ('a', 'b,c') -> ('a', 'b', 'c')

That means we can't do it when the call is forwarded, so this is only
done on the CLI. The UI already sends values as a tuple.

Replace escaping in the csv parser with quoting. Quoted strings can have
embedded commas instead of having to escape them. This prevents the csv
parser from eating all escape characters.

Also, document Param's csv arguments, and update tests.

https://fedorahosted.org/freeipa/ticket/2417
https://fedorahosted.org/freeipa/ticket/2227

ipalib/cli.py

@@ -1025,9 +1025,10 @@ class cli(backend.Executioner):
         if not isinstance(cmd, frontend.Local):
             self.create_context()
         kw = self.parse(cmd, argv)
-        kw['version'] = API_VERSION
         if self.env.interactive:
             self.prompt_interactively(cmd, kw)
+        kw = cmd.split_csv(**kw)
+        kw['version'] = API_VERSION
         self.load_files(cmd, kw)
         try:
             result = self.execute(name, **kw)